An easy-opening container closure of the full panel pull-out type has a panel removable from the container wall and a tab secured to the panel to effect the removal thereof. This type of easy-opening container usually has a front opening tab, i.e., a tab of the type in which the forward end or nose engages the container wall adjacent an edge of the removal panel to initiate severance of the panel from the container.
More particularly, easy-opening closures of this type typically include a rupturable scoreline in the container end panel defining the removable panel, a tab having a handle portion and a piercing portion, and a rivet integral with the panel for securing the tab to the removable panel. The piercing portion of the tab is at the forward or nose end of the tab and lies closely adjacent the rupturable scoreline.
In operation of this closure, the handle portion of the tab is moved away from the removable panel to force the piercing portion of the tab against the rupturable scoreline or against the removable panel closely adjacent the scoreline. As the tab is secured to the removable panel by the rivet, such upward movement of the handle portion thereof tends to flex the removable panel adjacent the rivet. As the upward movement of the handle portion continues, it eventually becomes necessary for a section of the panel to bend about a bend line to allow for full upward movement of the handle portion of the tab. With a longitudinally rigid tab the bend line forms intermediate the rivet and the center of the end panel. A problem arises in this connection in that it is relatively hard to bend such a large section of the panel about the bend line. Furthermore, large bend sections are generally undesirable in that they disturb the product within the container.
In an attempt to make easy-opening closures of this type more easily opened, it has been suggested to form a lance in the tab. The tab is then riveted to the container end panel through the lanced portion thereof. This lancing of the tab provides the tab with an integral bend line and reduces the bend section size; however, it does not obviate the need for forming a bend line fully across the section of the removable panel during panel removal. Furthermore, the lancing of the tab further complicates the tab construction and makes the tab subject to failure by tearing and otherwise.
It is often necessary or desirable to form a vent opening in an easy-opening closure before the initial severance of the removable panel from the end panel. Such vents may be desirable where the product within the container is under pressure or vacuum and it is wished to release or admit pressure prior to beginning removal of the panel.
Heretofore, such vent openings have been formed only with rear opening tabs, i.e., those tabs that are secured to a tear strip intermediate the ends of the tab and such intermediate portion of the tab lifts the leading edge of the tear strip to initiate severance thereof. One such device includes a complicated hinged tab arrangement secured to a tear strip in an end panel by a first rivet. The tab is further secured to the end panel by a vent rivet which is spaced from the first rivet and lies outside of the tear strip. When the tab is manipulated to open the container, the vent rivet is removed by a shearing action before the tab is operative to remove the tear strip from the end panel. This arrangement is fraught with disadvantages, among which are the complexity of the tab, the need for a second rivet, and the additional force required to remove the vent rivet by a shearing action. Furthermore, this prior art device would not be suited for use with a front opening tab.